Liberate-max_transition

Hi Fengye,

The min_output-cap is already very small. Are you sure your cell/model works fine at the give voltage? Does the error occur at all slew or just the max_transition? If increasing the max_transition works for some cells bu causes issue with other cells, you may have to use define_index command to change the slew or load table for other cells. You can get a template following the steps below,

1. use -auto-index -trial options in char_libarary command and generate a template library, with the max_transition that is the maximum of all the transitions.

2. use write_template to generate a template file

3. adding define_index commands to change the slew or load table on cell/pin basis.

Regards,

Guangjun

Hi, Guangjun, thanks for your reply.My cell can normally work at the given voltage 0.3V. I have simulated with Hspice. The error occur with the cell OAI21M0R, OAI21M1R,... The error information mainly concern about maximum load for the cell pin and min_output_cap. According to the reminder,if I increase the max_transition, the sequential cell D-flipflop will meet error for removal time.
I don't know how to set proper index value for the cell, so I choose the auto_index. I remember you said,"min_transition is the minimum transition of the cells in your library. max_transition can be defined based on the actual design the library is used for. "
Now, for this question, do I need to use define_index? How I can properly set the proper index value?
Hope to receive your reply in your free time.
Regars,
fengye

Hi Fengye,

If you remove define the index table manually without -auto_index, does the error still occur?

Thanks,

Guangjun

Hi, Guangjun. If I remove the auto_index from char_library, and I add ""

define_template -type delay \
-index_1 {12 22 37 50 60 70 80 90 100 110 120 } \
-index_2 {0.001 0.002 0.0035 0.005 0.0065 0.008 0.0095 0.011 0.0125 0.014 0.016 } \
delay_template_11x11

define_template -type power \
-index_1 {12 22 37 50 60 70 80 90 100 110 120 } \
-index_2 {0.001 0.002 0.0035 0.005 0.0065 0.008 0.0095 0.011 0.0125 0.014 0.016 } \
power_template_11x11

The new error occurs, like "ERROR (LIB-174): (char_library): The template 'delay_template_11x11' has an unreasonable '-index_1' slew value of: 100 nanoseconds which is greater than the sim_duration (1e-07 seconds). Update the 'define_template' and 'define_index' commands or the sim_duration in the Tcl script and rerun."

Hi,

with the slew index table, the max slew is 120ns, which is bigger than your sim_duration of 1e-7s. You may sue sim_duration to increase its value. you may also need to set sim_estimate_duration=0

Regards,

Guangjun

Hi,

After I set sim_duration =1e-5s, and  sim_estimate_duration=0, there is no error. But all the value of the table is casual, which may lead inaccurate library. I still don't know why it cannot work with auto_index, and max_transion=120n

Regards,

fengye

Hi, Guangjun,

The following are some warnings for the auto_index setting. 

.WARNING (LIB-411): An estimated max load value of 3.17381e-16F will be used for slew: '3.80423e-07s' pin: 'Z' of cell: 'AOI21M0R' because the auto_index algorithm failed to determine the max load using bisection. This can occur when the inside-view algorithm cannot determine a valid vector. Add appropriate 'define_arc' commands specific to pin 'Z' and rerun.
WARNING (LIB-411): An estimated max load value of 2.80317e-16F will be used for slew: '4.52601e-07s' pin: 'Z' of cell: 'AOI21M1R' because the auto_index algorithm failed to determine the max load using bisection. This can occur when the inside-view algorithm cannot determine a valid vector. Add appropriate 'define_arc' commands specific to pin 'Z' and rerun.

How should I set the proper index value?

Hi Fengye,

have you run Spectre simulation with the max slew and min/max load? do you see output transition within the range of slew index?

Regards,

guangjun

Hi, Guangjun,

   Thanks for your reply! Happy mid-autumn day to you!  I run hspice simulation for OAI21M0R with input slew=120n， load= 1fF, the output rise transition=42.3ns, fall transition=30.5ns，（from 10% to 90%). If the load=16fF, the output rise transition=265ns, fall transition=91ns.

The ouutput behaves the normal function. Is the maximum transition unreasonable? 

Regards,

fengye

Hi Fengye,

happy mid-fall day.

I suggest you not to use auto_index in this case.

Regards,

guangjun